People are generally aware of the most common causes of hallucinations, like schizophrenia and a really high fever. But lesser known are the more rare causes; here are six you probably haven't heard about.

Bulletproof Coffee Creator Dave Asprey Is Back With FATWater, Fat-Infused Water You Can Drink For 20 Calories

Dave Asprey, otherwise known as the man who successfully convinced your friends to drink coffee mixed with butter, is back with his latest invention: FATWater.

The fat-infused is positioned as a better way to both hydrate your body and burn more fat. The formula, Asprey claimed, is better than real water. He told the NY Daily News his formula stems from his previous career in Silicon Valley, where he focused on disruptive technology.

"This is disruptive technology for beverages," he said. Whether this “disruptive technology” actually leads to improved diet and health is still up for debate.

Asprey extracts fat from a coconut oil he's patented; then, he adds tiny droplets of it to his water. He suggests the fatty oil is what hydrates cells, because he's found body cells are more likely to absorb H2O molecules when they come with trace amounts of fat particles. Asprey also found that fat-infused water gives consumers an extra energy boost.

“The oils enhance thermogenesis, which is a fancy word for ‘fat burning’,” Asprey said. “They get burned as energy and have an appetite-suppression effect. It’s not like we put in sunflower oil or canola.”

How much fat is actually in each bottle? It's equal to two squares of Chocolove, a type of dark chocolate.

FATwater is currently only being sold in Asprey's Bulletproof Coffee Shop in Santa Monica, Calif., in addition to some Los Angeles-based natural food stores. He does hope, however, to soon sell his product nationwide.

Experts, on the other hand, are highly skeptical of Asprey’s new water revelation. Even though his claims may sound appealing, many nutritionists are saying his formula isn't based on real science. Dietitian and nutritionist Rochelle Sirota told NY Daily News that so far, she is not impressed.

“It is just getting crazier and crazier,” she said. “What is the need? Coconut water can be very hydrating because of the electrolytes, but I do not get this whole thing.”

To Martin Riese, the country’s only water sommelier (a fancy way to say tap water sampler), FATwater is "near water," at best.

“Water should not have calories and this has 20,” he pointed out. "I believe water should come from nature and not a factory.”

But despite this skepticism, and claims that he is going too far (just look at Whole Foods' failed asparagus water), Asprey stands by his product.

“Biohacking is taking control of the environment around you so you have control of your biology, so you are less stressed and recover better and are a nicer person,” he explained. “I am making it easier for people to make those changes and feel good all the time.”